Environmental regulations and general public awareness of the problems relating to the disposal of waste materials has led to attempts to use recycled waste material in a variety of applications.
One such waste material is fly ash. Fly ash refers to the fine particulate matter that is carried upward by hot gasses from the combustion of coal in energy-generating facilities. Fly ash is produced by such facilities in large quantities and most of the fly ash is captured and buried in landfills. There have been a number of attempts in the prior art to use fly ash in a variety of structural products.
U.S. Pat. No. 5,154,771 by Wada et al. discloses an inorganic composition which optionally includes Portland cement as a component, and it is disclosed that the Portland cement can include some fly ash. The composition further includes a polysaccharide, a molding aid, an optional reinforcing fiber and water.
U.S. Pat. No. 3,625,723 by Sicka discloses a method for making a cellular foam product that includes fly ash as the main ingredient. The fly ash is mixed with an aluminum phosphate solution, calcium silicate, aluminum hydroxide and a carbonate to prepare a foam which is dried to produce a structural product having a density of about 45 lb/ft.sup.3.
U.S. Pat. No. 5,366,548 by Riddle discloses a composition that includes fly ash which is useful for forming construction blocks. The grade of fly ash used in the invention is that which possesses pozzolanic (cement-like) behavior, such as Class C fly ash. The fly ash is mixed with kiln dust and water and high pressure is applied to form a brick.
U.S. Pat. No. 4,659,385 by Costopoulos et al. discloses a building material manufactured from fly ash, specifically, a light-weight cementitious building material. The composition includes fly ash, a bonding agent, an air entrainer and a foaming agent. It is disclosed that the structural product has the appearance of concrete and can be used like concrete and that the method for making the material is much like ordinary concrete.
Despite the foregoing, it would be useful to formulate a structural product predominately using waste materials, such as fly ash, wherein the structural product has good density and is useful as a building material. It would be advantageous if such a product was capable of receiving nails and screws without significant chipping or cracking and without predrilling pilot holes. It would be useful if the material was relatively light weight, yet strong enough to use as structural bricks. It would be useful if the product in the form of blocks could be attached seamlessly and was substantially fire resistant. It would be useful if such material could be easily milled into a variety of shapes using ordinary hand tools. It would be beneficial if the material substantially eliminated or reduced the need for and cost of wooden studs, insulation, mortar, exterior siding, combustible roofing or gypsum wall board. It would also be beneficial if the product could be made using an efficient and relatively inexpensive process.